dup_fd
fds = dup_fd(cur_fds, punch_hole);
struct files_struct *dup_fd(struct files_struct *, struct fd_range *) __latent_entropy;
newf = dup_fd(oldf, NULL);
fd = dup_fd(fd, NULL);
int dup_fd, pipe_fds[2];
dup_fd = dup(pipe_fds[0]);
ASSERT_GE(dup_fd, 0);
EXPECT_NE(pipe_fds[0], dup_fd);
ASSERT_EQ(filecmp(self, self, pipe_fds[0], dup_fd), 0);